1. Field of the Invention
The present invention generally relates to a method of forming a polyurethane foam from a resin component and an isocyanate component using at least one control valve controlling a flow rate of at least one of the resin component and the isocyanate component.
2. Description of the Related Art
Chemical foam compositions, such as polyurethane foams, are presently well known and used in a number of different applications. Polyurethane foams are useful in such applications as thermal insulation, marine floatation, coatings, and packaging. Polyurethane foams are formed by the mixture of a resin component and an isocyanate component.
The resin component and the isocyanate component are separately stored in tanks until use. The resin and isocyanate components are mixed in a foam dispensing apparatus and are dispensed therefrom as polyurethane foam. The tanks storing the resin component and the isocyanate component and the foam dispensing apparatus are pressurized to drive the resin and isocyanate components from the tanks and through the foam dispensing apparatus.
The tanks and the foam dispensing apparatus are pressurized by either a low pressure system or a high pressure system. The low pressure system uses gas pressure to pressurize the tanks and the foam dispensing apparatus. The low pressure system operates in a pressure range of 100-500 psi (pounds per square inch) and creates a flow rate of 0.4-5 gpm (gallons per minute) for each of the resin and isocyanate components, i.e., the low pressure system can dispense polyurethane foam at a flow rate of 6-10 gpm. Because the low pressure system is pressurized by gas and operates at relatively low pressures, the low pressure system is relatively small and therefore relatively easy to transport and maneuver. In addition, the low pressure system is relatively inexpensive to manufacture. However, the flow rate of the polyurethane being dispensed from the foam dispensing apparatus is relatively low, which disadvantageously increases the amount of time to dispense a given amount of polyurethane foam.
The high pressure system operates in a pressure range of 1500 to 6000 psi and creates a flow rate of each of the resin and isocyanate components of 4-50 gpm, i.e., the high pressure system can dispense polyurethane foam at 8-100 gpm. However, high pressure systems include large pumps and a large amount of relatively thick pipes. As a result, high pressure systems are disadvantageously large and therefore are difficult to transport and maneuver. In addition, high pressure systems are very expensive relative to low pressure systems.
It would be advantageous to develop a method which allows for the dispersion of polyurethane foam at a relatively high flow rate while maintaining the foam dispensing apparatus at a relatively small size and a relatively inexpensive cost to manufacture.